The invention relates to dental prostheses in general, and more particularly to improvements in attachments which serve to connect stationary and removable components of dental prostheses. Still more particularly, the invention relates to improvements in devices which are used to releasably lock male and female detent members of attachments serving to connect removable and stationary components of dental prostheses to each other.
Commonly owned published European patent applications Nos. 136 671 and 263 235 and the aforementioned commonly owned U.S. Pat. Nos. 4,586,902 and 4,773,859 disclose attachments which employ complementary male and female detent members one of which is mounted in or on the stationary component and the other of which is mounted on or in the removable component of a dental prosthesis. The attachment further comprises a device which serves to releasably lock the detent member for the removable component to the detent member for the stationary component when the two detent members assume predetermined positions relative to each other, i.e., when the removable component is in an optimum position relative to the stationary component of the dental prosthesis. For example, the female detent member can be provided with one or more grooves to slidably receive one or more complementary parts of the male detent member, and the detent member which is provided on the removable component can be locked to the other detent member by a spring which is confined in a flat housing and a portion of which can snap into a complementary recess. The recess is provided in one of the detent members and the housing for the spring is provided on or in the other detent member. The spring can resemble the letter S or the numeral five and can be made of resilient metallic wire. Problems can arise when the spring and/or its housing must be cleaned to remove confined saliva and/or fragments of food and/or other foreign matter which is likely to undergo fermentation and can generate undesirable odors. Moreover, the spring and its housing are very small so that they cannot be readily manipulated by the wearer of the dental prosthesis. This means that the wearer must visit a dentist at frequent intervals for the sole purpose of having the detent members and the locking device for the movable detent member inspected and/or cleaned.
The published European patent application No. 263 235 discloses the possibility of replacing the aforementioned S-shaped or like wire spring with a block of silicone rubber which completely or nearly completely fills the flat housing of the locking device and carries a wear-resistant metallic element capable of entering a complementary recess in order to lock the movable detent member to the other detent member. The block prevents or reduces the likelihood of penetration of saliva, fragments of food and/or other foreign matter into the housing. However, the useful life of a locking device which employs a block of silicone rubber or a like material is relatively short and, ,moreover, a rubber block is less appetizing in the mouth than a spring of steel wire or the like. The published European patent application No. 263 235 further proposes to use a wear-resistant element in the form of a solid cylinder with two coaxial stubs which are rotatably mounted in the block of silicone rubber or the like. It has been found that proper mounting of stubs in the elastic block presents many problems and, therefore, such locking device was never actually made and/or used.